This is the La Mesa Depot, part of the Pacific Southwest Railway Museum in La Mesa. The station was originally called the Allison Station, and although the station currently resides at its original site, the building has been moved several times over the years since its construction in 1894 and has been used for other purposes such as an antique store, a worm farm and a chicken coop according to the museum's website. You can check out more details at http://www.sdrm.org/la-mesa/.